Couplings are widely used in various general machineries for connecting two shafts and transmitting torque and motion, so that the two shafts rotate synchronously. Traditional couplings requires interconnection between a driving shaft and a driven shaft to transmit torque, which has complicated structure and requires high manufacturing precision, and damage of components is easily caused by overload. Especially, when the driving shaft and the driven shaft need to work in two different media that are isolated from each other, a sealing member must be used for dynamic seal, and as a result, either that the rotation resistance needs to be increased to ensure reliable seal, or that the seal is not tight enough to prevent leakage. In addition, along with wear and aging of the sealing member, the leakage would become more serious, and especially in a system where a harmful gas (or liquid) exists, the leakage would contaminate the environment and endanger lives.
A magnet coupling, which is a non-contact coupling with a structural form that is different from traditional couplings, utilizes a brand new principle of magnetic interaction to transmit force and torque between a driving shaft and a driven shaft without direct contact, and is able to convert dynamic seal into static seal with zero leakage. Therefore, magnet couplings are widely used on occasions that have special requirements against leakage, and have entered a massive commercialization stage.
According to different setting locations of interacting magnets, magnet couplings are classified into planar magnet couplings and coaxial magnet couplings. Currently, coaxial magnet couplings on the market have the following basic structure: steel magnets are respectively mounted on an inner rotor and an outer rotor, the inner rotor is fixed on a load shaft, and the outer rotor is fixed on a driving shaft. Because the steel magnets are generally made of magnetic material with strong magnetism, commonly used magnet couplings is extremely inconvenient to install and adjust due to influence of magnetic force thereof. In order to cope with the aforementioned problem, the structure of magnet coupling is designed such that the inner and outer rotors are connected as a whole, for example, Chinese patent literature CN103904860A discloses a sleeve-type permanent-magnet vortex coupling that has its inner and outer rotors connected by a bearing, however, such a bearing causes increased structural complexity and product cost of the coupling, and when the two rotors rotate together during operation of the coupling, once slipping occurs due to eccentricity between the rotors, direct friction between the steel magnets on the two rotors would damage the steel magnets and even damage the entire coupling device, and on the other hand, if the two rotors are attracted to stick together accidentally during mounting, it is extremely difficult to separate the two rotors, especially for magnet couplings which transmits a large torque, e.g., for a magnet coupling that transmits a torque of thousands of Newton-meter, the attraction force of its rotors “sticking” together is tens of thousands Newton. Because of the aforementioned reasons, the magnet couplings of prior art is inconvenient to install and adjust and is unsuitable to be popularized.